Method and apparatus for sweating waxes



1945. F. HEDERHORST METHOD AND APPARATUS FOR SWEATING WAXES 4 Sheets-Sheet 1 Filed Dec. 26, 1941 Jan. 30, 1945. F. HEDERHORST METHOD AND APPARATUS FOR SWEATING WAXES Filed Dec. '26, 1941 4' Sheets-Sheet 2 PICKUP Flat-I Jim! 7% Jan. 30, 1945. F, H R' T 2,368,468

METHOD AND APPARATUS FOR SWEATING WAXES Filed Dec. 26, 1941 4 Sheets-Sheet 3 Jan. 30, 1945. F. HEDERHORST METHOD AND APPARATUS FOR SWEATING WAXES 4 Sheets-Shet 4 Filed Dec. 26, 1941 Far-Z4 Patented Jan. 30, 1945 METHOD AND APPARATUS FOR SWEATING WAXES Fred- Hederhorst, Baytown, Tex., assignor to Standard Oil Development Company, a corporation of Delaware Application December 26,1941, Serial No. 424,414

' 18 Claims.

The present invention relates to improvements in the art of refining petroleum wax ,and in par- .ticular it relates to improvements in a continuous process for sweating crude wax recovered customarily by refrigerating, and centrifuging, settling or filtering.

Prior to my invention, the conventional method for producing a finished wax from a crude wax by the. so-called sweating process involved melting the wax and discharging it into sweating pans where it was solidified and supportedon perforated plates or screens. The pans were first filled with water to levels just above the screens and the unsweated wax was run in and floated upon the Water sothat, after coolingand withdrawing the water, the solidified wax rested upon the screens. Heated air Was then circulated over. the pans and, as the sweating of the wax began, the temperature of the heated air was slowly increased so that the temperature of the wax increased gradually, and increasingly higher melting fraction of the wax slowly melted, flowed through the remaining crystals of. wax, and dropped through the supporting screens into the ans-from whence the molten fractions, or foots oil, were withdrawn. The temperature of the pans was ultimately held at atemperature slightly below that of the desired melting point of the wax for a time period of from to 20'hours to provide ample opportunity for the foots oil to run out of the resulting crude scale or crystalline wax. The sweated wax was then meltedby further raising the temperatureand was. run off for storage or further treatment. Approximately to '72- hours were required to. complete. the sweating cycle, actual sweating time beingabout 65% of the total. The process .above described is of the intermittent type, obviously, and is a ve'ry time-consuming operation.

Speaking generally at first, my invention relates to a'continuous method for sweating wax and,v in. its essence, involves rotating a cylindrical filter slightly immersed in a pan of the. crude molten wax, whereupon a layer of the molten wax is deposited. on the outer surface of the cylinder and, as the filter rotates, the layer of wax is gradually heated to a maximum temperature, during .which timev the oil and lower melting point waxes flow through the. crystalline wax toward the axis of the rotating drum, the: flow of waxbeing. aidedby suction or pressure, and finaly the. foots oil and low melting point wax are withdrawn from the system. However an. important feature of my invention involves applying heat to the layer v of wax undergoing sweating on the surface of the drum by circulating a heating. medium in close. proximity to the wax, the cinculation. of the heat.- ing fluid being controlled by the operation of a master valve, axially disposed. on. the end of the drum. However, an important feature of. my invention resides-inthe concept of heating or cooling the layer of. wax deposited on the drum as desired, all. of which. willmore fully. appear hereinafter.

My inventionv will be best understood by reference to the accompanying. dra'wings which show diagrammatically a suitable apparatus in which my invention. may be carried into effect.

Fig. 1 is a sidevi-ew. of my improved sweating apparatus shown in position in a. pan, contain.- ing molten waxv to be. sweated';

Fig. 2 is an end. view of the drum. (across sections II--II,. Fig. 1) illustrating theproduct discharge flow, the drum being in position in a pan containing molten wax;

Fig. 3 is also an end view of ,the drumlacross sections III--III, Fig. 1) illustrating the temperature control duringv the'cooling and. heating cycles of the sweating operation; I

Fig. 4 is the rotatable portion of a. master valve disposed. at one end of the drum concentrically with respect-to. the axis. thereof;

Fig. 4A is the stationary portion of the maste valve corresponding to .the rotatable. portion shown inFig. 4; I

Fig. 5 is the rotatableportion of a master valvewhich isdisposedat the opposite end of the drum from the first mentioned master valve, and is also concentrically disposed. with respect to the axis thereof; and

Fig. 5A is a stationary portion of thevalve corresponding to that shown in Fig. 5.

Similar reference characters refer to similar parts throughout the several views.

Referring in detail to the. drawings, I represents a. cylindricalv drum. supported by. suitable standards 2 and immersing, as. shown, into a feed bowl 3 containingv a, quantity of. crude molten wax 4.. The drum. is. rotated by any suitable driving means, not shown, such as an electric motor. Peripherally disposed. along the entire length of the drum a coil of pipe ll)v is provided to conduct a heating or cooling fluid in close proximity to the outer surface of the drum. The coil of pipeis supported on a foraminous member, such as a screen H, or preferably, as shown more fully in Fig. 2., ahoneycombed grill. 'Finned tubes or any other suitable arrangement to provide maximum heat distribution may also be used. As shown in the drawings, the'screen or grill work'is spaced apart from the outer surface of the drum proper, forming an annular space l4. (See Fig. 1.)

Referring in particular to Fig. 2 in the modification which I have chosen to illustrate my invention, the drum is internally divided into 12 sectors, S, by spaced radially disposed plates 5.

It will be understood, however, that a greater or lesser number of such sectors may be employed.

The annular space between the screen or grill.

work and the surface of the drum is in communication in each sector through a pipe I! with the rotating part of a master valve 20, so that, as will presently -appear, foots oil may be withdrawn from the annular space l4 through said pipe 11, thence through the master valve 20, and rejected from the sweating device, while finished wax may be similarly withdrawn through a pipe in communication with the said master valve. In order to explain this operation more fully,

reference is again had to Fig. 2 where I have shown the drum l immersed. in the molten wax 4. The immersed portion of the drum acquires a layer of molten wax, approximately an inch in thickness. This wax is deposited on tubes or grill work in the area represented in the drawings by A by virtue of the chilling and solidifying action of a cooling medium, circulating in tubes I 8. The water circulating in the tubes may be of a temperature of about 80 F., and ordinarily this will produce a layer of wax approximately one inch thick. The solidified wax then emerges from the molten wax and passes through the region represented by B in Fig. 2. During this phase of the operation, the wax is neither heated nor cooled, but in the third phase, that is, the phase represented by C, the wax is gradually heated by means of warm water at a temperature from about 90 F. to about 140 F. During this heating operation, the foots oil and lower melting point wax fractions are withdrawn from the higher-melting wax toward the center of the drum, first passing into annular space M and thence through one of the pipes I1, depending upon the particular position-of the wax as it moves through this phase. When a port 25 of the rotatable portion of the master valve (see Fig. 5) is in registry with port 21 of the nonrotatable portion of the mastervalve, the foots oil or low melting point wax fraction is withdrawn through its corresponding pipe I! and discharged from the system through said port 21.

Referring again to Fig. 2, when the time arrives that a portion of wax has reached the point D, the sweating and removal of the undesirable portions of the crude wax has been substantially completed. In order to aid in the flow of foots oil, or low melting point wax, from the crystalline wax, vacuum may be applied at port 21 (see Fig. 5) or the drum.may be enclosed in a closed shell, of somewhat larger internal diameter than the drum, and pressure may be applied by pumping a gas into the annular space between the surrounding shell and the drum. A combination of both expedients may be employed. The pressure drop across the layer of wax may vary from 1 to 50 #/sq. in., preferably from about 2 to 5 #/sq. in.

The purified crystalline wax then passes through the phase represented by D. During the passage of the cake through the phase D, the pipe I! is out of communication'with a port in a stationary portion of the master valve. Thereafter, the cake passes into the phase represented by E, where it is again heated, preferably by circulating very hot water or steam through pipes ID, the degree of heat supplied depending upon the melting point of the wax, since in this phase the wax is melted. Simultaneously the molten wax discharges from the system through port 28 when drain pipes l1 and their corresponding ports 25 in the rotatable portion of the master valve come into registry with port 28 of the nonrotatable portion of the master valve. The last phase of the operation is represented'by F on the drawings (Fig. 2) and, as in the case of phases D and B, the pipe I! and its corresponding port in the rotatable portion of the master valve is out of registry or communication with the port in the non-rotatable portion of the master valve. The same is true with respect to the phase represented by A, where the drum acquires the aforementioned layer of crude wax to be sweated.

' I shall now describe the method of circulating the heating or cooling medium through pipes Ill previously referred to. The circulation of these heating or cooling media through the pipes is controlled by the master valve shown in Figs. 4 and 4A. As previously indicated, the portion of the valve shown in Fig. 4 is the rotatable portion, and it will be noted that there are 24 ports in this portion, as compared with 12 in the corresponding valve portion (Fig. 5) controlling the flow of foots oil and wax from the system. During the period when the wax is being picked up, that is, during the phase A (Fig. 3) cold water is introduced from some outside source, not shown, into inlet port 35 of the stationary portion of the control valve, circulates through pipes 18 to tubes ID, and is withdrawn through pipes I9 in communication with outlet port 36 of the stationary portion of the control valve. During the phase B (Fig. 3), the cooling tubes 10 are out of communication with an outside source of fluid. During the phase C, where, as previously described, the wax was heated up to a temperature of about 140 F. and the heating is effected by introducing hot water, heated at least to a temperature of 140 F., through port in the stationary part of the control valve, thence through pipe l8, thence through tubes 1 0, thence to pipe l9, thence into port 56 in the stationary portion of the master valve, thence through pipe 52 into port 55, thence through pipe I8A to coil ill-A, thence through coil lflA to pipe l9-A, to port 58 in the non-rotatable portion of the master valve, thence through pipe 58 to port 60 in the said non-rotatable portion, thence through pipe Ill-B, thence to coil Ill-,-B, thence through pipe l9-B to port 65. In like manner,

the hot water is introduced through port 66, circulates through pipe IBC, coil HlC, pipe l9C, and is withdrawn from the system through port 61. During the phase D, the coil H] is out of communication with any outside source of fluid. In phase E, the wax, as previously described, is melted and withdrawn from the system through port 28 (see Fig. 5). The steam necessary to melt the wax is introduced into the system through port 10 and is withdrawn through port '12, steam circulating through the coil 10 and the communicating pipes being entirely analogous to that already described in connection with the circulation of the water in phase A.

In phase F, the coil I0 is out of communication with an outside fluid.

.I have found that best results are obtained by rotating; drum I at a: speed of from to 4 revolutions per hour; With respect tothe thickness of the layer of wax deposited on the drum in phase A, I have found: that good results are ob-, tamed by so manipulating the process that the wax layer is from about to 2- inches thick. F urthermorafl have found that; good sweating temperatures lie in. the range of; about 90 to 140 F: A convenient and economical sizeof the drum i's'onewhich has a diameter of about8- ftgand 'a length ofl about 15ft:

" liiany mod-il'ications of my invention maybe made by those-skilled in the: art, In the modification which Ihave chosen to illustrate, it will be noted that I'haveshown two sections employed inthe chilling of the molten wax in feed bowl 3 four sections employed in sweating the wax,

wax by gravitmisupplemented: by: the, application of vacuum across the layer of: heated wax,there;-

and three sections employed in melting the wax.- I may vary the number of sections: thus employed q in any of the foregoing operations, responsiveg of the desired product;

-' The: present invention having: been thus describedfiand illustrated, what is claimed as new and useful and is desired to be secured by Letters Patent is: I

1 A continuous process for sweating waxwhich to the melting point-of the charge and the quality v after further heating the wax; from which the normally liquid and low melting: pointf'ractions have beer'r removed in order: to liquefy said: last named wax, and recovering said; last named: wax as a purified product in liquid form 6. The process, set forth in claim 5 inwhich the: drum: is; rotated at a velocity of from about to 4 revolutionsperhour.

'7 .Y The process: set forth. in claim 5 in which,

during the removal of normally liquid: and low I said shaft, a pipe connecting the foraminous comprises depositing a film of" crude wax on a rotating surface, gradually heating the wax, withdrawing foots oil and low melting point waxes by maintaining a pressure differential across the wax layer, and recovering the residual wax of improved quality from said rotating surface.

which comprises melting the crude wax',,continuously depositing a layer of said wax on a'rotating surface, heating said wax at'a temperature within the range of from about 90 to 140 Fl, withdrawing foots oil" and low meltin point 'wax fractions from the crude wax by gravity; supe plemented by maintaining a pressure difieren tial across the wax layer, and thereafter recovering the residual crystalline wax'of improved quality from said rotating surface. f

3. The process set forth in claim 2 in which the'pressure differential maintained across the wax layer during the withdrawal of the "foots oil and low melting point wax fractions is fro about 1 to 50 #/sq.in.

4. The process set forth in claim 2 in which, during the heatingoperation, the wax is in inti- 2'. An improved process for obtaining crystallin'e wax of improved quality fromqcrude wax,

mate indirect heat exchange relationship witha heating fluid.

5. An improved method for sweating slack wax to facilitate the removal of "foots oil and low outer surface of said drum, causing a heating fluid to fiow in close proximityto the layer .I of

- wax deposited on the drum'over an area removed from the immersed portion of said drum to facilitate liberation of liquid and low boiling frac- "tions contained within the crude wax, withdrawing the said liberated fractions from the crude surfaceof said drumwith said master valve, a second master'valve disposed on the shaft at the endofthe drum'opposite that at'whioh the first named master valve is disposed, conduit pipes disposed peripherallyabout the foraminous surfaceof said drum, pipes in communication with said peripherally disposed pipes-and said second named master valve adapted to conduct a liquid from outside the drum totheperip'herally' disposed pipes, and means for causing rotation of said drum 9'. The apparatus set-forth in claim 8 in which i the foraminous surface of thedrum comprises a honeycombed 'grillwork in which disposed finned tubes are imbedded.

10. An improved method for sweating slack wax 'to facilitate the removal of foots oil and l'o-w'smeltin'g point wax" fractions and to obtain a peripherally crystalline wax of improved quality, which comprises providing a body of molten crude wax in a' feed zen-e, causing an enlarged drum to-rotate in contacting relationship with the molten wax in such a manner that a portion of the drum is continuously submerged in the molten wax, causing a cooling fluid to flow through that portion of the drum in contacting relationship with the molten wax to chill a portion of said wax below .its melting point and deposit a layer of said wax on the outer surface of said drum, causing a heat ing fluid to flow in close proximity to the layer'of wax deposited on the drum over an area removed from the immersed portion of said drum to facilitate liberation of liquid and low boiling fractions contained within the crude wax, Withdrawing the said liberated fractions from the crude wax [by gravity, supplemented by the application of pressure across the layer of heated wax, thereafter further heating the wax from which the normally liquid and low melting point fractions have been removed in order to liquefy said last named wax,

and recoverin said last named wax as a purified product in liquid form.

11. A method for sweating slack wax to facilitate the removal of foots oil and low melting point wax fractions and to obtain a crystalline wax of improvedquality, which comprises establishing a pool of slack wax in molten condition, continuously passing through said pool a body having a surface cooled to a temperature substantially below the temperature of the pool to thereby form'a layer of wax on said surface, continuously moving said deposited layer of wax out of said pool, applying heat to'said surface grade ually after the removal of said wax from said pool, establishing a pressure gradient across said layer of wax to force out of it: any foots oil and low melting point Wax liquefied by said heat and subsequently removing the layer of sweated wax from said surface.

- 12. An apparatus for the sweating of slack wax, comprising a receptacle adapted to hold a pool of molten slack wax, a body adapted to move through said receptacle in such a manner as to be at least partially immersed in said pool of wax, means for moving said body through said receptacle, means for cooling at least that portion of the surface of said body arranged to be immersed in the pool of slack wax while said surface is passing through said receptacle and means for heating said surface after it has emerged from said receptacle.

13. An apparatus for the sweating of slack wax which comprises a rotating body, means arranged on the periphery of said body for receiving a layer of slack wax and disposing said layer of wax sothat it has an inner surface and an outer surface, means for establishing a pressure differential across said layer of wax and means for applying heat to said layer of wax.

14. An apparatus for the sweating of slack wax comprising a rotatable .body, a plurality of receptacles formed on the periphery of said body, means arranged peripherally on said body for supporting a layer of slack wax in fluid communication with said receptacles in such a manner as to provide an inner surface and anouter SUI! face on said layer of wax, means for establishing a pressure differential across said layer of wax, means for applying heat to said layer of wax and means for withdrawing fluid from said receptacles.

15. An apparatus for the sweating of slack wax comprisin a receptacle adapted to hold a pool of molten slack wax, a framework composed of hollow tubes arranged in the form of a grill mounted for movement through the pool of wax in said receptacle, means for moving said framework through said pool, means for supplying a cooling medium to said tubes while they are passing through said pool of slack wax and means for replacing said cooling medium by a heating medium after said tubes have emerged from said 9001 of slack wax.

16. An apparatus for the sweating of slack wax comprising a receptacle adapted to hold a pool of molten slack wax, a rotatable body mounted for partial immersion in said pool of slack wax, a grill work of hollow tubes arranged peripherally on said body, means for rotating said body, means for supplying a coolin fluid to said tubular members whil they are immersed in said wax, means for automatically replacing said cooling fluid by a heating fluid after said tubular members emerge from said pool of slack wax and means for continuously removing wax from said tubular members.

17. An apparatus for continuously sweating slack wax comprising a receptacle adapted to hold a pool of molten slack wax, a rotatable body mounted for :partial immersion in said pool,

means for rotating said body continuously, a plurality of receptacles arranged on the periphery of said body, a grill Work of tubular members arranged peripherally on said body and overlying said receptacles, means for continuously drawing off fluid from said receptacles, means for supplying fluids of different temperature to said tubular members, and means for controlling the type of fluid supplied such that a cooling fluid is supplied to said tubular members while they are immersed in said pool of slack wax, heating fluid of gradually increasing temperature is supplied to said tubular members shortly after they emerge from said pool of slack wax and there after hotter heating fluid capable of melting sweated wax is supplied to said tubular members.

18. An apparatus according to claim 17 in which said tubular members are provided with fluid conducting inlet tubes and means are provided for connecting the latter successively with a source of cooling fluid and in order with sources of successively hotter heating fluids.

FRED HEDERI-IORST. 

